1. Field of the Invention
The present invention relates generally to a projection device, and more particularly to a projector and a projecting lens of the projector.
2. Description of the Related Art
With advancement in technology, projectors have become the most popular devices used in a presentation. A projecting lens in a projector is the most important element to clearly show images on a screen. In order to use the projector in a limited space, short-throw projection is a common requirement in the modern projector. A conventional projecting lens for short-throw projection usually has a lot of large lenses to obtain short-throw projection and high optical performance.
Therefore, the size and weight of the conventional projecting lens for short-throw projection conflicts with the current design focus of projectors, which is miniaturization and lightweight. Besides, it takes a high cost to manufacture the conventional projecting lenses because of their sizes.
In order to improve the above drawback, a rear-projection projector is provided in the market. The rear-projection projection is provided with a reflector to reflect the image beam of the projector to a screen. Such rear-projection projector does not provide focusing function, so that the screen must be placed at a preset location, which has a fixed distance from the projector. It is unadjustable to meet the environment where the projector is going to project the image. In conclusion, the conventional projector and its projecting lens still need to be improved.